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		<title>three.js webgl - particles - sprites</title>
		<meta charset="utf-8">
		<meta name="viewport" content="width=device-width, user-scalable=no, minimum-scale=1.0, maximum-scale=1.0">
		<link type="text/css" rel="stylesheet" href="main.css">
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	<body>

		<div id="info">
			<a href="https://threejs.org" target="_blank" rel="noopener">three.js</a> - webgl particle sprites example<br/>
			snowflakes by <a href="http://en.wikipedia.org/wiki/File:Sketch_of_snow_crystal_by_Ren%C3%A9_Descartes.jpg">Ren&eacute;  Descartes</a>
		</div>

		<script type="module">

			import * as THREE from '../build/three.module.js';

			import Stats from './jsm/libs/stats.module.js';

			import { GUI } from './jsm/libs/dat.gui.module.js';

			let camera, scene, renderer, stats, parameters;
			let mouseX = 0, mouseY = 0;

			let windowHalfX = window.innerWidth / 2;
			let windowHalfY = window.innerHeight / 2;

			const materials = [];

			init();
			animate();

			function init() {

				camera = new THREE.PerspectiveCamera( 75, window.innerWidth / window.innerHeight, 1, 2000 );
				camera.position.z = 1000;

				scene = new THREE.Scene();
				scene.fog = new THREE.FogExp2( 0x000000, 0.0008 );

				const geometry = new THREE.BufferGeometry();
				const vertices = [];

				const textureLoader = new THREE.TextureLoader();

				const sprite1 = textureLoader.load( 'textures/sprites/snowflake1.png' );
				const sprite2 = textureLoader.load( 'textures/sprites/snowflake2.png' );
				const sprite3 = textureLoader.load( 'textures/sprites/snowflake3.png' );
				const sprite4 = textureLoader.load( 'textures/sprites/snowflake4.png' );
				const sprite5 = textureLoader.load( 'textures/sprites/snowflake5.png' );

				for ( let i = 0; i < 10000; i ++ ) {

					const x = Math.random() * 2000 - 1000;
					const y = Math.random() * 2000 - 1000;
					const z = Math.random() * 2000 - 1000;

					vertices.push( x, y, z );

				}

				geometry.setAttribute( 'position', new THREE.Float32BufferAttribute( vertices, 3 ) );

				parameters = [
					[[ 1.0, 0.2, 0.5 ], sprite2, 20 ],
					[[ 0.95, 0.1, 0.5 ], sprite3, 15 ],
					[[ 0.90, 0.05, 0.5 ], sprite1, 10 ],
					[[ 0.85, 0, 0.5 ], sprite5, 8 ],
					[[ 0.80, 0, 0.5 ], sprite4, 5 ]
				];

				for ( let i = 0; i < parameters.length; i ++ ) {

					const color = parameters[ i ][ 0 ];
					const sprite = parameters[ i ][ 1 ];
					const size = parameters[ i ][ 2 ];

					materials[ i ] = new THREE.PointsMaterial( { size: size, map: sprite, blending: THREE.AdditiveBlending, depthTest: false, transparent: true } );
					materials[ i ].color.setHSL( color[ 0 ], color[ 1 ], color[ 2 ] );

					const particles = new THREE.Points( geometry, materials[ i ] );

					particles.rotation.x = Math.random() * 6;
					particles.rotation.y = Math.random() * 6;
					particles.rotation.z = Math.random() * 6;

					scene.add( particles );

				}

				//

				renderer = new THREE.WebGLRenderer();
				renderer.setPixelRatio( window.devicePixelRatio );
				renderer.setSize( window.innerWidth, window.innerHeight );
				document.body.appendChild( renderer.domElement );

				//

				stats = new Stats();
				document.body.appendChild( stats.dom );

				//

				const gui = new GUI();

				const params = {
					texture: true
				};

				gui.add( params, 'texture' ).onChange( function ( value ) {

					for ( let i = 0; i < materials.length; i ++ ) {

						materials[ i ].map = ( value === true ) ? parameters[ i ][ 1 ] : null;
						materials[ i ].needsUpdate = true;

					}

				} );

				gui.open();

				document.body.style.touchAction = 'none';
				document.body.addEventListener( 'pointermove', onPointerMove );

				//

				window.addEventListener( 'resize', onWindowResize );

			}

			function onWindowResize() {

				windowHalfX = window.innerWidth / 2;
				windowHalfY = window.innerHeight / 2;

				camera.aspect = window.innerWidth / window.innerHeight;
				camera.updateProjectionMatrix();

				renderer.setSize( window.innerWidth, window.innerHeight );

			}

			function onPointerMove( event ) {

				if ( event.isPrimary === false ) return;

				mouseX = event.clientX - windowHalfX;
				mouseY = event.clientY - windowHalfY;

			}

			//

			function animate() {

				requestAnimationFrame( animate );

				render();
				stats.update();

			}

			function render() {

				const time = Date.now() * 0.00005;

				camera.position.x += ( mouseX - camera.position.x ) * 0.05;
				camera.position.y += ( - mouseY - camera.position.y ) * 0.05;

				camera.lookAt( scene.position );

				for ( let i = 0; i < scene.children.length; i ++ ) {

					const object = scene.children[ i ];

					if ( object instanceof THREE.Points ) {

						object.rotation.y = time * ( i < 4 ? i + 1 : - ( i + 1 ) );

					}

				}

				for ( let i = 0; i < materials.length; i ++ ) {

					const color = parameters[ i ][ 0 ];

					const h = ( 360 * ( color[ 0 ] + time ) % 360 ) / 360;
					materials[ i ].color.setHSL( h, color[ 1 ], color[ 2 ] );

				}

				renderer.render( scene, camera );

			}

		</script>
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